An example will be taken of manufacture of an epitaxial wafer by growing an epitaxial layer upon a substrate wafer. The flatness of the resulting epitaxial wafer may be determined by adding the thickness of the epitaxial layer to the shape of the surface of the substrate wafer. If there are variations in the flatness of the substrate wafer and for the thickness distribution of the epitaxial layer, then variations occur in the flatness of the final manufactured product. In order to manufacture an epitaxial wafer of high flatness, then increase of the flatness of the substrate wafer and increase in the uniformity of the epitaxial layer thickness are required. However, since it is difficult to obtain an ideal state for both of these, an effective method has been to combine the surface shape of the substrate wafer with a layer thickness profile which is matched thereto, as described in Patent Reference #1.
Patent Reference #1: Japanese Patent Publication 2007-94132.
According to a method of combining concave shapes and convex shapes as disclosed in Patent Reference #1, it is possible to improve the flatness over the use of a random method. However, since there are various types of shape of substrate wafers for different wafers, variation of the flatness occurs even when combination like that described above is performed. For example, if the characteristics of the shape of the substrate wafers are determined by lot units, then it is not possible to cancel out variations in flatness due to differences in the shapes of different wafers within the same lot.
Furthermore, according to the invention disclosed in Patent Document #1, while it is possible to select the combination which yields the highest flatness, it is not known whether or not it has been possible to satisfy the required flatness specification.
Yet further, according to the invention disclosed in Patent Reference #1, attention is only given to the flatness at the border portion of the wafer. However, the flatness at regions other than the border portion also changes according to growth of the epitaxial layer. Thus, the invention disclosed in Patent Reference #1 is unsatisfactory from the point of view of enhancing the flatness over the entire area of the wafer.
Related problems are not limited only to flatness when growing an epitaxial layer upon a wafer; they are present in relation to changes of the surface shape of a wafer which occur along with various types of processing, such as bending of a wafer along with layer growth, change of the shape of the surface of the wafer when that surface is ground or etched, and the like.
Accordingly, the object of the present invention is to enhance the surface profile of a manufactured semiconductor wafer over substantially its entire area.